No abstract

Objectives. Ethoxylated bisphenol A dimethacrylate (bisEMA) is a base monomer in several dental resin composites. It was the main aim of the present study to determine if bisEMA can reach the dental pulp by generally passive diffusion through the coronal dentinal tubules stimulated via eluent liquids surrounding the root structures only. Methods. In 20 human third molar teeth, standard Class-I occlusal cavities were prepared and provided either with an adhesive system alone or additionally with a composite restoration, according to the instructions of the manufacturer. The teeth were placed in an elution chamber such that the elution media only came into contact with the tooth root/tooth base where they were incubated at 37 °C for up to 7 d. Samples were taken after 1, 2, 4 and 7 d. Gas chromatography/mass spectrometry was used to identify bisEMA and other monomers in ethanol/water (3:1) and aqueous eluates. Results. bisEMA was only found in ethanol/water eluates, where the teeth had received a composite restoration. Traces of bisEMA with up to three ethylene oxide units could be detected in these eluates. Depending on the dentin thickness, different elution kinetics of bisEMA were determined. Regardless of the treatment of teeth, triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol dimethacrylate (TEEGDMA) were found in ethanolic/aqueous eluates in equal amounts. Most TEGDMA and TEEGDMA diffused through the dentin within the first 24 h. Significance. Depending on the dentin layer thickness, bisEMA was released for varied time periods, resulting in varied concentrations and exposure times for the different cells of the dental pulp. The concentrations of TEGDMA and TEEGDMA were greatest for cells of the dental pulp within the first 24 h.

No abstract

No abstract

No abstract

No abstract

No abstract

Determination of Coplanar Polychlorinated Biphenyls in Mineral Oils and Waste Oils Due to insufficient waste management polychlorinated biphenyls (PCB) are often found in waste oils and in recycled mineral oil products. Because of their structure coplanar PCBs are more toxic than other congeners and insofar possibly comparable to polychlorinated dioxins and furans (PCDD/F). Known analytical methods for PCBs in mineral oils do not distinguish between the different toxic congeners. This paper describes a method of selective measurement of eleven coplanar PCBs from mineral oils. The complexity of the matrix and the very low concentration of the analytes require a laborious clean‐up procedure: Solid phase extraction (SPE) on silica impregnated with sulfuric acid, gel permeation chromatography, direct treatment with conc. sulfuric acid and chromatography on alumina. After separation of the co‐planar congeners from the other PCBs by chromatograpy on activated charcoal and on basic alumina they are determined by GC/high‐resolution‐MS.